A conventional pitching device known to applicant is disclosed in Taiwanese utility patent application No. 88206273 and includes a frame with four sides. One of any two opposite sides of the frame has a plurality of emitting devices and the other side has receiving devices. The emitting devices each emit infrared rays to the corresponding receiving device on the opposite side so as to define a plurality of longitudinal rays and latitude rays, which define a net portion. The pitcher is required to pitch a ball through the frame and when the ball passes through the net portion, some of the infrared rays are interrupted so that the information is transferred to a CPU to display scores on a display board. However, the infrared rays emitting devices or the receiving devices are expensive so that the price of the pitching practice device will not be affordable for general players. Furthermore, the display board cannot show the velocity of the ball.
The present invention intends to provide a pitching practice device which includes simple parts and deformable strings so that when balls hit the strings, the displacement provides efficient data for the CPU to calculate the speed of the balls.